1. Field of the Invention
The present invention relates to an ignition equipment for light ignition thyristors, and particularly to an ignition equipment for thyristor valves in which light ignition thyristors are utilized.
2. Description of the Prior Art
Equipments which have heretofore been proposed as such type of ignition equipments have the following disadvantages. In this connection, FIG. 1 is a block diagram showing a conventional ignition equipment for light ignition thyristors in which an ignition circuit 1 generates an ignition signal S.sub.1 and transmits this ignition signal S.sub.1 to a photoelectric conversion circuit 2. This photoelectric conversion circuit 2 converts the aforesaid ignition signal S.sub.1 into light, and such light is transmitted, as a thyristor ignition light signal S.sub.2, to a plurality of light thyristors 3 being connected in series with the photoelectric conversion circuit 2, respectively. Furthermore the aforesaid photoelectric conversion circuit 2 is connected in series with light thyristors 3 through light guides 4, respectively. Moreover the aforesaid thyristors 3 are connected to a main circuit (not shown) through electric conductors 5 of the main circuit. In addition, a light emitting element 6 is connected in parallel to both ends of a series circuit consisting of a plurality of thyristors 3 via a resistance 7 for limiting current. The light emitting element 6 converts reverse voltage applied between an anode and cathode of each of the thyristors 3 into a light signal S.sub.3 in response to the reverse voltage, and the resulting light signal S.sub.3 is transmitted to a light receiving circuit 9 via a light guide 8. The light receiving circuit 9 converts the aforesaid reverse voltage detection light signal S.sub.3 into an electrical signal S.sub.4, and this electrical signal S.sub.4 is fed back to the ignition circuit 1.
Operation of the aforesaid ignition equipment will be described in detail hereinbelow.
First, in the case where reverse voltage is applied across an anode and cathode of each of the thyristors 3 in the thyristor series circuit, current flows through the light emitting element 6 via the resistance 7 for limiting current. As a result, the light emitting element 6 generates the reverse voltage detection signal S.sub.3, and the reverse voltage detection signal S.sub.3 thus generated is transmitted to the light receiving circuit 9 through the light guide 8. The electrical signal S.sub.4 derived from the light receiving circuit 9 is fed back to the ignition circuit 1.
Transmission of the thyristor ignition electrical signal S.sub.1 generated in the ignition circuit 1 to the photoelectric conversion circuit 2 is interrupted while reverse voltage is applied across an anode and cathode in each of the thyristors 3 by means of the thyristor reverse voltage detection electrical signal S.sub.4 fed from the light receiving circuit 9. Accordingly, the thyristor ignition electrical signal S.sub.1 is converted into light by means of the photoelectric conversion circuit 2 so far as reverse voltage is not applied to the thyristors 3. And such light is given to the respective thyristors 3 as the thyristor ignition light signal S.sub.2 to ignite simultaneously all the thyristors 3 so that current flows through the electric conductors 5 in the main circuit.
In such conventional equipment as stated above, there is a scattering in respect of a quantity of reverse recovery charge (hereinafter referred to simply as "Q.sub.rr ") in every thyristor 3. For this reason, there arises a scattering in respect of a period of time during which reverse voltage is applied across an anode and cathode of each of the thyristors 3. In spite of this fact, the thyristors have simultaneously been ignited with each other without taking such scattering of the period of time into consideration in a conventional equipment so that there is such a disadvantage in that a gate signal is applied to some of a plurality of the thyristors 3 to which reverse voltage has already been applied.
Furthermore a conventional equipment utilizes the light emitting element 6 and the light guide 8 in order to transmit the reverse voltage detection signal S.sub.3, and as a result there is also such a disadvantage in that its response is slow (because insulation must be kept for such extra components).
In addition, such conventional equipment also involves indispensably the light receiving circuit 9 for receiving the reverse voltage detection light signal S.sub.3 to convert the same into the electrical signal S.sub.4 and the light guide 8 for transmitting the reverse voltage detection light signal S.sub.3, thus the circuit construction of the equipment became complicated.